1. Field of the Invention
The present invention relates to testing machines, and more particularly to testers for testing printed circuit boards.
2. Description of the Related Art
Automatic testing machines have generally been found to be effective for use in testing printed circuit boards of various types. Such testing machines are particularly useful when testing large quantities of identical printed circuit boards, such as computer motherboards.
A typical tester used for testing printed circuit boards comprises a cover and a base. A control panel is formed on a front wall of the base. A retaining device, such as a fixture, is provided on a top wall of the base, for retaining a printed circuit board to be tested. The cover is parallelepiped-shaped, and is pivotably attached to the base. A knob is formed on a front wall of the cover, for opening and closing the cover. When testing a printed circuit board, an operator has to lift open the cover with the knob, fix the printed circuit board on the retaining device, and close the cover to start the test. However, such manual operation is slow, laborious and inefficient.
It is important for a tester to be able to accurately position a printed circuit board relative to a plurality of testing devices within the tester. Taiwan Patent Publication No. 483655 discloses a printed circuit board fixture comprising a base and a plurality of positioning pins. Each positioning pin comprises a pair of small ends and a large shaft between the small ends. The base defines a plurality of holes therein, and bottom ends of the positioning pins are inserted in the holes of the base respectively. The printed circuit board defines a plurality of positioning holes therein. Top ends of the positioning pins extend through the positioning holes of the printed circuit board. The printed circuit board is thereby supported on the shafts of the positioning pins.
The above testers incorporating typical printed circuit board fixtures are suitable for conventional motherboards that consist of a printed circuit board and a plurality of electrical components mounted thereon. However, many recently developed motherboards have highly complicated circuitry patterns and numerous electrical components mounted thereon. This requires the motherboard to be mechanically strong enough to hold the components securely. Therefore, a reinforcing plate is mounted to a solder side of the motherboard. The reinforcing plate functions only as a strengthening device. Therefore, the reinforcing plate is generally manufactured and installed with relatively low precision, to reduce manufacturing costs and save time.
However, this imprecision gives rise to a problem in the testing procedure. Because the reinforcing plate is not precisely mounted, it is frequently not parallel to the motherboard. The testing devices in the typical tester have predetermined positions relative to the conventional motherboard, not to the new type of motherboard having the reinforcing plate. As a result, it is problematic to position the new type of motherboard relative to the testing devices.
Thus the typical tester is not suitable for the new types of motherboard. When testing components such as I/O ports and sockets on the new type of motherboard, an operator has to manually attach or detach testing devices to or from the motherboard. Such manual operation is slow, laborious and inefficient. Furthermore, the motherboard is liable to be inadvertently damaged when handled by the operator.